The present invention relates generally to aircraft gas turbine engines with thrust augmentors and, more specifically, gas turbine engines including side-initiated augmentors.
Today's high performance aircraft typically include an augmented turbine-based propulsion system, such as a turbofan gas turbine engine having an afterburner or augmentor, for providing additional thrust during supersonic flight. The turbofan engine typically includes in downstream serial flow communication, a multistage fan, a multistage compressor, a combustor, a high-pressure turbine powering the compressor, and a low-pressure turbine powering the fan. A bypass duct surrounds and allows a portion of the fan air to bypass the multistage compressor, combustor, high pressure, and low-pressure turbine.
During operation, air is compressed in turn through the fan and compressor and mixed with fuel in the combustor and ignited for generating hot combustion gases that flow downstream through the turbine stages that extract energy therefrom. The hot core gases are then discharged into an exhaust section of the engine that includes an augmenter or afterburner from which they are discharged from the engine through a variable area exhaust nozzle.
Augmentors are located in exhaust sections of engines that include an exhaust casing and an exhaust liner circumscribing a combustion zone. Typically, augmentors include fuel injectors (such as spraybars or v-gutters) and flameholders that are mounted between the turbines and the exhaust nozzle for injecting additional fuel during reheat operations. The injection of additional fuel provides burning in the augmentor and produces additional thrust. Thrust augmentation or reheat using such fuel injection is referred to as wet operation, while operating dry refers to operation conditions where thrust augmentation is not used. In a typical augmentor configuration, the annular bypass duct extends from the fan to the augmentor for bypassing a portion of the fan air around the core engine to the augmentor. This bypass air is mixed with the core gases and fuel from the spraybars and ignited and combusted prior to discharge through the exhaust nozzle. The bypass air is also used in part for cooling the exhaust liner.
Current augmentor designs, such as the above mentioned spraybars and v-gutter designs include components that penetrate the engine flowpath. Augmentor components in the engine flowpath, or gas stream, inherently cause flow losses and reduced engine efficiency. Several modern gas turbine engine's and designs include radially extending spray bars and flameholders in an effort to improve flame stability and reduce losses in the engine flowpath. Radial spray bars disposed between radial flameholders having integrated radial spray bars have been incorporated in the GE F414 and GE F110-132 aircraft gas turbine engines. This arrangement provides additional dispersion of the fuel for more efficient combustion, but does not solve the issue of elimination structure protrusions into the engine flowpath that result in pressure drops.
When an augmented engine operates without the augmentor fueled, or during dry operation, the augmentor components penetrating the engine flow path obstruct the flow therein and create a pressure drop reducing thrust produced by the engine and increasing fuel consumption. Although providing an increased amount of thrust (for short durations), the performance penalty in the pressure drop associated with the typical augmentor fuel injectors and flame stabilizer hardware that is located within the engine flowpath is significant.
Accordingly, there is a need to provide for an engine augmentor that provides an increase in thrust that maintains augmentor performance while minimizing pressure losses in an engine flow path. It is therefore an object of this disclosure to provide for an augmentor that operates without augmentor components impinging on the engine flowpath in a gas turbine engine.